1. Field of the Invention
The present invention relates to a ripping device, and particularly to a ripping device that is used for ripping hard soil and soft rocks as a rear implement for use in an earthworking machine.
2. Description of the Prior Art
A prevailing type of a conventional ripping device was a ripper assembly of four-joint link type in which arms are coupled between lower portions of brackets provided at a vehicle body rear portion of a bulldozer and a lower portion of a beam provided with shanks, and in which hydraulic tilt cylinders are mounted between upper portions of the brackets and an upper portion of the beam. In such a ripping device, hydraulic lift cylinders for coupling the brackets and the beam were mounted between the arms and the hydraulic tilt cylinders. The tilt cylinders are mainly used for moving the shanks backward and forward, and the shaft cylinders for moving the shanks up and down. The brackets are provided at two spots rearward of the vehicle body to be symmetric to the right and left, wherein the brackets and the beam are coupled through the cylinders and the arms as described above, and the shanks was driven by means of total four cylinders. However, in such a conventional type ripping device, upper end positions of the brackets were set to be higher than the rear portion of the vehicle body since it was necessary to set base end portions of the lift cylinders higher for securing lifting force. This arrangement would cause the bracket upper portions or cylinders to hinder the field of view of the operator to make back work difficult. The repairability was also worsened in that detaching of a fuel tank at a rear portion of the vehicle body was difficult due to the presence of the brackets. Since two cylinders and arms exist within an identical vertical place with respect to a traveling direction when seen from the top of the vehicle body, interference of movements of the cylinders or those of the cylinders and the arms would occur so that operating ranges of a ripper tip mounted to a tip end of the shanks could not be expanded for the purpose of preventing interference.
It is known for a device of improved visibility (see, for instance, Japanese Utility Model Registration No. 2,544,731). The ripping device as illustrated in Japanese Utility Model Registration No. 2,544,731 is arranged in that a height of the brackets is set to be lower than a height of a rear portion of the vehicle body of a bulldozer, and in that bottom-sided base ends of the lift cylinders are aligned in parallel with bottom-sided base ends of the tilt cylinders whereupon they are pivotally attached to the brackets by means of the same pins. A tip end of the rod of the tilt cylinders is pivotally attached to an upper end of the beam while a tip end of the rod of the lift cylinders is pivotally attached to somewhat upward of a spot at which the arm is pivotally attached to a lower end of the beam. In Japanese Utility Model Registration No. 2,544,731, rearward visibility in and operability of repair are improved by setting the height of the brackets lower than the height of the rear portion of the bulldozer vehicle body, and by arranging the base end of the tilt cylinders and the base ends of the lift cylinder to be coaxial and pivotally attaching both by the same pins, cuts in costs of parts can be achieved.
Incidentally, the prior art example of Japanese Utility Model Registration No. 2,544,731 employs a structure in which a four-joint link is comprised by the tilt cylinders and the arms, and wherein the lift cylinders are mounted inside of the four-joint link when seen from a side with respect to a traveling direction of the vehicle body. Accordingly, a problem is provided that thrust of the lift cylinders will be extremely large when performing lifting movements of the ripper tip, which are movements of the ripper that require the largest cylinder thrust so that it will be necessary to set a large thrust spec for the cylinders which will result in a growth in size of the entire device. Moreover, since the bottom-sided based end of the tilt cylinders and the bottom-sided base of the lift cylinders are coaxial in the structure of Japanese Utility Model Registration No. 2,544,731, drawbacks are presented in that the operating range of the ripper tip will be restricted due to the necessity of avoiding interference of respective cylinders. The rearward visibility was also still worsened since a total of four cylinders were employed with alignments of the cylinders being symmetrical to the right and left.
The present invention has been made for solving the above-described conventional problems, and it is an object thereof to provide a ripping device that can be downsized with respect to a conventional ripper and that is capable of expanding the operational range of a ripper tip. It is also an object of the present invention to provide a ripping device that is capable of improving rearward visibility.